When AS is suspected your doctor will examine your spine, noting its posture and mobility and look for evidence of disease in other parts of your body. The three diagrams of the pelvis illustrate what can happen over a period of several years.
Before the disease: showing normal joints between thesacrum and upper pelvis, or ilium. There is also normal spacing between each vertebra. In some people (especially those with teenage onset) hip joints can be affected, but such involvement is relatively rare.
The diagnosis of AS is confirmed byX-rays. The characteristic changes are in the sacroiliac joints, but they may take many months to develop and may not be obvious during the first consultation. There is some disagreement as to whether you can have characteristic symptoms before radiological change, or whether, once the patient actually gets to the doctor and has an X-ray, changes have occurred. The doctor may also ask for a blood test, which may illustrate how active the disease is. This is called an ESR, showing the sedimentation rate. Sometimes anaemia can occur. In some cases, especially where there might be some doubt about the diagnosis, the doctor may ask for the HLA B27 antigen to be tested. If present, the diagnosis could be supported. If HLA B27 is not present, AS is very unlikely but not impossible (24:1 against, for those who gamble!)
The condition takes a different course in different people and no two cases are exactly the same. The symptoms will come and go over many years. However, sometimes it does go into remission. In the classic case, the lumbar spine can become stiff, caused by the growth of additional bone, as can the upper spine and neck. There is evidence that the patient can play a significant part in influencing how serious this becomes. People with AS must, throughout this period, pay constant attention to their posture to avoid the forward stoop associated with the condition.